Method and apparatus for transmitting and receiving he ra su ppdu in a wlan

ABSTRACT

A method for transmitting data by a first station (STA) in a wireless local area network (WLAN) system is disclosed. The method includes configuring, as a radio frame for transmission of the data, a high efficiency extended range single user physical protocol data unit (HE ER SU PPDU) in which a high efficiency signal A (HE-SIG-A) field is repeated, and transmitting the configured HE ER SU PPDU to a second STA in a resource unit (RU) of one of a first type and a second type, the first type having a size of 106 tones and the second type having a size of 242 tones. If the HE ER SU PPDU is transmitted in an RU of the first type, the HE ER SU PPDU is transmitted in an RU of the first type at a fixed position in a primary 20-MHz channel.

CROSS REFERENCE

Pursuant to 35 U.S.C. §119(e), this application claims the benefit ofU.S. Provisional Application No. 62/349,610, filed on Jun. 13, 2016 and62/350,188, filed on Jun. 15, 2016, the contents of which are all herebyincorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to a wireless local area network (WLAN),and more particularly, to a method and apparatus for transmitting andreceiving a high efficiency extended range single user physical protocoldata unit (HE ER SU PPDU) in a WLAN.

Discussion of the Related Art

Although a frame transmission method as proposed below is applicable tovarious wireless communication systems, it will be described in thecontext of a WLAN system as an exemplary system to which the presentdisclosure is applicable.

Standards for WLAN technology have been developed as institute ofelectrical and electronics engineers (IEEE) 802.11 standards. IEEE802.11a and b use an unlicensed band at 2.4 GHz or 5 GHz. IEEE 802.11bprovides a transmission rate of 11 Mbps and IEEE 802.11a provides atransmission rate of 54 Mbps. IEEE 802.11g provides a transmission rateof 54 Mbps by applying orthogonal frequency division multiplexing (OFDM)at 2.4 GHz. IEEE 802.11n provides a transmission rate of 300 Mbps forfour spatial streams by applying multiple input multiple output(MIMO)-OFDM. IEEE 802.11n supports a channel bandwidth of up to 40 MHzand, in this case, provides a transmission rate of 600 Mbps.

The above-described WLAN standards have evolved into IEEE 802.11ac thatuses a bandwidth of up to 160 MHz and supports a transmission rate of upto 1 Gbits/s for 8 spatial streams and IEEE 802.11ax standards are underdiscussion.

A station (STA) conforming to the IEEE 802.11ax standard may be referredto as a high efficiency (HE) STA, and a physical layer radio frame usedin a HE system may be referred to as a HE physical protocol data unit(HE PPDU).

Each element of a PPDU available in the HE system will be describedbelow.

FIG. 1 is a view referred to for describing initial discussion of eachelement of a HE PPDU.

In IEEE 802.11ax, a legacy 1× symbol structure (3.2 μs) may be adoptedfor a part of a frame up to HE-SIGs (HE-SIG A and HE-SIG B), and a framestructure having a 4× symbol (12.8 μs) structure may be used forHE-preamble and Data of the frame, as illustrated in FIG. 1. Unlesscontradicting the following description, there is no problem withapplying the present disclosure even though the above structure ischanged.

An L-part may be configured as in a legacy wireless fidelity (Wi-Fi)system, and thus may include a legacy short training field (L-STF), alegacy long training field (L-LTF), and a legacy signal (L-SIG).Generally, the L-SIG preferably carries packet length information. AHE-part is a new part configured for the IEEE 802.11ax standard (HighEfficiency). HE-SIGs (HE-SIG A and HE-SIG B) may be interposed betweenthe L-part and a HE-STF, providing common control information anduser-specific information. Specifically, the HE-SIGs may be configuredseparately as HE-SIG A for providing common control information andHE-SIG B for providing user-specific information.

Although the above HE PPDU format is applicable to all datatransmissions of a STA, it is preferred to make a slight modification tothe HE PPDU format according to a transmission state of the STA in orderto increase system efficiency.

SUMMARY OF THE INVENTION

Accordingly, an aspect of the present disclosure is to provide physicalprotocol data unit (PPDU) formats available in a high efficiency (HE)system, particularly a method for transmitting and receiving a highefficiency extended range single user physical protocol data unit (HE ERSU PPDU), when a robust transmission is needed.

Additional advantages, objects, and features of the present disclosurewill be set forth in part in the description which follows and in partwill become apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of thepresent disclosure. The objectives and other advantages of the presentdisclosure may be realized and attained by the structure particularlypointed out in the written description and claims hereof as well as theappended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the disclosure, as embodied and broadly described herein, amethod for transmitting data by a first station (STA) in a wirelesslocal area network (WLAN) system is disclosed includes configuring, as aradio frame for transmission of the data, a high efficiency extendedrange single user physical protocol data unit (HE ER SU PPDU) in which ahigh efficiency signal A (HE-SIG-A) field is repeated, and transmittingthe configured HE ER SU PPDU to a second STA in a resource unit (RU) ofone of a first type and a second type, the first type having a size of106 tones and the second type having a size of 242 tones. If the HE ERSU PPDU is transmitted in an RU of the first type, the HE ER SU PPDU istransmitted in an RU of the first type at a fixed position in a primary20-MHz channel.

The radio frame for transmission of the data may include a HE singleuser (SU) PPDU, a HE multi-user (MU) PPDU, and a HE trigger-based PPDUin addition to the HE ER SU PPDU. If the data is transmitted in the HEMU PPDU or the HE trigger-based PPDU, an RU of a third type having asize of 26 tones and an RU of a fourth type having a size of 52 tonesmay be used in addition to an RU of the first type and an RU of thesecond type.

If the data is transmitted in the HE ER SU PPDU, an RU of the third typeand an RU of the fourth type may not be used.

If the data is transmitted in the HE SU PPDU, a bandwidth (BW) field ofthe HE-SIG A field may indicate a transmission BW of the HE SU PPDUamong BWs being multiples of 20 MHz. If the data is transmitted in theHE ER SU PPDU, the BW field of the HE-SIG A field may indicate whetherthe HE ER SU PPDU uses an RU of the first type or an RU of the secondtype.

The data may be transmitted in a data field of the HE ER SU PPDU in arepeated transmission scheme in which available resources of the datafield are divided into two parts and the same information is repeatedlytransmitted twice. In this case, the HE-SIG A field may include a 1-bitfield indicating whether the repeated transmission scheme is applied tothe data field.

If the data is transmitted in the HE SU PPDU, a modulation and codingscheme (MCS) field of the HE-SIG A field may indicate an applied MCSlevel in 4 bits. If the data is transmitted in the HE ER SU PPDU, theMCS field of the HE-SIG A field may represent only three or fewer MCSlevels.

In another aspect of the present disclosure, a STA for transmitting datain a WLAN system includes a processor for configuring, as a radio framefor transmission of the data, a high efficiency extended range singleuser physical protocol data unit (HE ER SU PPDU) in which a highefficiency signal A (HE-SIG-A) field is repeated, and a transceiver fortransmitting the configured HE ER SU PPDU. The transceiver transmits theHE ER SU PPDU in an RU of one of a first type and a second type, thefirst type having a size of 106 tones and the second type having a sizeof 242 tones, and if the HE ER SU PPDU is transmitted in an RU of thefirst type, the processor controls transmission of the HE ER SU PPDU inan RU of the first type at a fixed position in a primary 20-MHz channel.

The radio frame for transmission of the data may include a HE SU PPDU, aHE MU PPDU, and a HE trigger-based PPDU in addition to the HE ER SUPPDU. If the data is transmitted in the HE MU PPDU or the HEtrigger-based PPDU, the processor may use an RU of a third type having asize of 26 tones and an RU of a fourth type having a size of 52 tones inaddition to an RU of the first type and an RU of the second type.

If the data is transmitted in the HE ER SU PPDU, the processor may notuse an RU of the third type and an RU of the fourth type.

If the data is transmitted in the HE SU PPDU, a BW field of the HE-SIG Afield may indicate a transmission BW of the HE SU PPDU among BWs beingmultiples of 20 MHz. If the data is transmitted in the HE ER SU PPDU,the BW field of the HE-SIG A field may indicate whether the HE ER SUPPDU uses an RU of the first type or an RU of the second type.

The processor may transmit the data in a data field of the HE ER SU PPDUin a repeated transmission scheme in which available resources of thedata field are divided into two parts and the same information isrepeatedly transmitted twice.

The HE-SIG A field may include a 1-bit field indicating whether therepeated transmission scheme is applied to the data field.

If the data is transmitted in the HE SU PPDU, an MCS field of the HE-SIGA field may indicate an applied MCS level in 4 bits. If the data istransmitted in the HE ER SU PPDU, the MCS field of the HE-SIG A fieldmay represent only three or fewer MCS levels.

It is to be understood that both the foregoing general description andthe following detailed description of the present disclosure areexemplary and explanatory and are intended to provide furtherexplanation of the present disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of thepresent disclosure. In the drawings:

FIG. 1 is a view referred to for describing initial discussion of eachelement of a high efficiency physical protocol data unit (HE PPDU);

FIGS. 2 and 3 are views illustrating a HE single user (SU) PPDU formatand a HE multi-user (MU) PPDU format, respectively, among HE PPDUformats which may be used in an embodiment of the present disclosure;

FIG. 4 is a view illustrating a HE trigger-based PPDU format among HEPPDU formats which may be used in an embodiment of the presentdisclosure;

FIGS. 5 and 6 are views illustrating an uplink (UL) MU transmissionscheme and a DL MU transmission scheme, respectively to describe anapplication example of each HE PPDU format;

FIG. 7 is a view illustrating a high efficiency extended range singleuser physical protocol data unit (HE ER SU PPDU) format according to anembodiment of the present disclosure;

FIG. 8 is a view illustrating a structure of HE-SIG A in a HE SU PPDUused in an embodiment of the present disclosure;

FIG. 9 is a view illustrating a tone allocation scheme used in a HEsystem;

FIG. 10 is a view illustrating a bandwidth (BW) field of HE-SIG Aaccording to an embodiment of the present disclosure;

FIG. 11 is a view illustrating the concept of including, in HE-SIG A, afield indicating whether a repeated transmission scheme is applied to aData field of a HE ER SU PPDU according to an embodiment of the presentdisclosure;

FIG. 12 is a view illustrating modulation and coding scheme (MCS)information in HE-SIG A of a HE ER SU PPDU according to an embodiment ofthe present disclosure;

FIG. 13 is a table illustrating a structure of HE-SIG A in a HE ER SUPPDU according to an embodiment of the present disclosure; and

FIG. 14 is a block diagram illustrating exemplary configurations of anaccess point (AP) (or base station (BS)) and a station (STA) (or userequipment (UE)) according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent disclosure with reference to the accompanying drawings. Thedetailed description, which will be given below with reference to theaccompanying drawings, is intended to explain exemplary embodiments ofthe present disclosure, rather than to show the only embodiments thatcan be implemented according to the present disclosure.

The following detailed description includes specific details in order toprovide a thorough understanding of the present disclosure. However, itwill be apparent to those skilled in the art that the present disclosuremay be practiced without such specific details. In some instances, knownstructures and devices are omitted or are shown in block diagram form,focusing on important features of the structures and devices, so as notto obscure the concept of the present disclosure.

High Efficiency Physical Protocol Data Unit (HE PPDU) Types andIntroduction of High Efficiency Extended Range Single User PhysicalProtocol Data Unit (HE ER SU PPDU)

FIGS. 2 and 3 are views illustrating a HE single user (SU) PPDU formatand a HE multi-user (MU) PPDU format among HE PPDU formats which may beused in an embodiment of the present disclosure;

A high efficiency (HE) system supports an SU transmission mode and an MUtransmission mode. The HE SU PPDU illustrated in FIG. 2 may be used inthe SU transmission mode, and the HE MU PPDU illustrated in FIG. 3 maybe used in the MU transmission mode.

The HE SU PPDU does not need to include HE signal B (HE-SIG B) among thefields described with reference to FIG. 1 because HE-SIG B is used totransmit user-specific control information in the MU transmission mode,as described before. In the HE SU PPDU format, HE-SIG A is Bus long asillustrated in FIG. 2 and does not need to be repeated on a symbolbasis, compared to a later-described HE ER SU PPDU.

Meanwhile, the HE MU PPDU illustrated in FIG. 3 is used in the MUtransmission mode. The HE MU PPDU format may include HE-SIG B totransmit user-specific control information. The HE MU PPDU may alsoinclude an 8-us HE-SIG-A field.

FIG. 4 is a view illustrating a HE trigger-based PPDU format among HEPPDU formats which may be used in an embodiment of the presentdisclosure.

Aside from a HE MU PPDU used in the MU transmission mode as illustratedin FIG. 3, a HE trigger-based PPDU may be used as a PPDU transmitted inresponse to a trigger frame triggering uplink (UL) MU transmission,received from an access point (AP). Accordingly, a HE MU PPDU may beused mainly for downlink (DL) MU transmission as described later,whereas a HE trigger-based PPDU as illustrated in FIG. 4 may be used forUL MU transmission.

The HE trigger-based PPDU format illustrated in FIG. 4 is identical tothe HE SU PPDU format illustrated in FIG. 2 in terms of the structuresof legacy short training field (L-STF), legacy long training field(L-LTF), legacy signal (L-SIG), and HE-SIG-A fields, and different fromthe HE SU PPDU format in that the former may include a 8-us HE-STF fieldas illustrated in FIG. 4.

FIGS. 5 and 6 are views illustrating a UL MU transmission scheme and aDL MU transmission scheme, respectively to describe an applicationexample of each HE PPDU format.

Specifically, FIG. 5 illustrates a UL MU transmission situation.Referring to FIG. 5, an AP may transmit a trigger frame on DL toschedule UL MU transmission of a plurality of STAs. The trigger framemay include scheduling information based on which the plurality of STAstransmit HE trigger-based PPDUs. Therefore, each STA may transmit a HEtrigger-based PPDU as illustrated in FIG. 5. The HE trigger-based PPDUis configured in the manner described with reference to FIG. 4. The APmay transmit an acknowledge/negative acknowledgement (ACK/NACK) inresponse to a UL MU data transmission in the HE trigger-based PPDU.While the AP is shown as transmitting a block ACK (BA) in FIG. 5, the APmay use a general ACK frame, a BA frame, or a multi-STA BA frame of aformat common to the plurality of STAs in order to acknowledge ornegative-acknowledge the UL MU data transmissions.

FIG. 6 illustrates a DL MU transmission situation. Referring to FIG. 6,an AP may transmit DL data in a HE MU PPDU to a plurality of STAs duringan acquired transmission opportunity (TXOP). The HE MU PPDU may includean aggregated MAC (medium access control) protocol data unit (A-MPDU)directed to each STA, as illustrated in FIG. 6. The HE MU PPDU used forDL MU transmission may be configured in the format illustrated in FIG.3.

Each STA may transmit an ACK/NACK in the form of a BA in response toreception of the HE MU PPDU, as illustrated in FIG. 6. Schedulinginformation is required to enable each STA to transmit an ACK/NACK inMU. While a trigger frame may be separately used for scheduling, the HEMU PPDU transmitted by the AP may include scheduling information for BAtransmission, as illustrated in FIG. 6, thereby increasing efficiency.

FIG. 7 is a view illustrating a HE ER SU PPDU format according to anembodiment of the present disclosure.

For SU transmission, a HE SU PPDU may be used, as illustrated in FIG. 2.However, a STA needs a more robust type of transmission to extendcoverage in a specific case in the HE system. A HE ER SU PPDU has beenproposed to cover such an extended range, as illustrated in FIG. 7.

The HE ER SU PPDU may have the following features.

To ensure the reliability and robust transmission of HE-SIG A, thesymbols of HE-SIG A are preferably repeated once and transmitted. InFIG. 7, HE-SIG A is 16 us long, which implies that each symbol of HE-SIGA in the HE SU PPDU of FIG. 2 is repeated once.

Further, it is preferred to boost the power of L-STF, L-LTF, HE-STF, andHE-LTF of the HE ER SU PPDU by 3 dB relative to L-STF, L-LTF, HE-STF,and HE-LTF of the HE SU PPDU, for robust performance against a channel.

The HE ER SU PPDU is transmitted on a 20-MHz primary channel, andpreferably supports only one spatial stream (SS) and specific modulationand coding schemes (MCSs) (e.g., MCS0, MCS1, and MCS2). This simplifiesthe transmission structure of the HE ER SU PPDU used for robusttransmission, and transmission of the HE ER SU PPDU with boosted poweris favorable.

Based on the basic idea of a HE ER SU PPDU, a method for transmittingand receiving a HE ER SU PPDU will be described below in detail.

HE ER SU PPDU Transmission Scheme and Specific Configuration of HE-SIG A

Considering that a HE ER SU PPDU is a special case of a HE SU PPDU, thefollowing description will be given of the difference between a HE SUPPDU transmission scheme and a HE ER SU PPDU transmission scheme.

FIG. 8 is a view illustrating a structure of HE-SIG A in a HE SU PPDUused in an embodiment of the present disclosure.

In the HE SU PPDU, HE-SIG A includes 1-bit information indicatingwhether the PPDU is for UL transmission or DL transmission. HE-SIG Afurther includes 1-bit format information indicating whether the PPDU isa HE trigger-based PPDU or a HE SU PPDU.

A bandwidth (BW) field of HE-SIG A may be 2 bits long to indicate thetransmission BW of the HE SU PPDU among 20 MHz, 40 MHz, 80 MHz, and 160MHz. An MCS field may indicate a used MCS level in 4 bits.

The information illustrated in FIG. 8 has been defined in 50 bits, withthe usage of 2 bits not defined.

Now, a description will be given of a method for transmitting andreceiving a HE ER SU PPDU based on the above-described information of aHE SU PPDU, and a configuration of HE-SIG A as signalling informationfor the method.

IEEE 802.11ax regulates data transmission in OFDMA as mandatory, anddefines four types of resource units (RUs) as listed in [Table 1] below,for DL/UL transmission in a 20-MHz BW.

FIG. 9 is a view illustrating a tone allocation scheme used in a HEsystem.

[Table 1] below lists RU sizes and the numbers of RUs in 20 MHz by type,when tones are allocated in the manner illustrated in FIG. 9.

TABLE 1 Number of RUs in Size of RU 20 MHz 26-tone RU 9 52-tone RU 4106-tone RU 2 242-tone RU 1

For example, if data is transmitted in a HE MU PPDU and a HEtrigger-based PPDU, the above four types of RUs may be available.Therefore, when a HE ER SU PPDU is transmitted in OFDMA according to anembodiment of the present disclosure, the four types of RUs may also beconsidered.

In this context, the following three approaches are considered.

(1) Method 1

All of the four types of RUs may be available in transmitting a HE ER SUPPDU. That is, one of the four RU sizes (types) is selected and data istransmitted in an RU of the selected size during ER PPDU transmission.

(2) Method 2

Only the 52-tone, 106-tone, and 242-tone RU types are used, among thefour types of RUs.

(3) Method 3

Only the 106-tone or 242-tone RU type is used, among the four types ofRUs.

(3) Method 4

Only the 242-tone RU type is used, among the four types of RUs.

In a preferred embodiment of the present disclosure, a HE ER SU PPDUtransmission scheme based on Method 3 among the four approaches is used.The reason for preferring an RU of a large size among the available fourtypes of RUs is that the use of a large RU requires less signallinginformation than use of a small RU and thus transmission is simplified,which is suitable for a HE ER SU PPDU for robust transmission.

However, if only the 242-tone RU type is used as in Method 4, a functionof transmitting a signal adaptively according to a channel state is notviable, which is inefficient for robust transmission of a HE ER SU PPDU.

Further, the preferred embodiment of the present disclosure proposes atransmission scheme in which only 242-tone and 106-tone RUs are used asdescribed before, and when 106 tones are used in 20 MHz, a HE ER SU PPDUis transmitted at a fixed position, thus obviating the need foradditional signalling of the resource position. Therefore, if 106 tonesare used, a HE ER SU PPDU is transmitted in a fixed 106-tone RU inprimary 20 MHz, without the need for additional signalling.

Specific configurations of HE-SIG A under the above assumption will bedescribed below.

Embodiment of Transmitting HE ER SU PPDU in 106-Tone/242-Tone RU atFixed Position

Another advantage of selectively using 106 tones or 242 tones for a HEER SU PPDU is that the selection may be indicated simply by 1-bitcontrol information. As described before, since the HE ER SU PPDU istransmitted in an RU type selected between the 106-tone RU type and the242-tone RU type in primary 20 MHz, 2-bit information of the BW field ofthe HE ER SU PPDU, described with reference to FIG. 8, may not beneeded.

Therefore, the unnecessary BW field may be reused to indicate whetherthe RU type is 106 tones or 242 tones in an embodiment of the presentdisclosure.

FIG. 10 is a view illustrating a BW field in HE-SIG A according to anembodiment of the present disclosure.

Referring to FIG. 10, the BW field of a HE SU PPDU indicates one of 20MHz, 40 MHz, 80 MHz, and 160 MHz in 2 bits. On the other hand, only twoout of four cases represented by a 2-bit BW field of a HE ER SU PPDU mayindicate whether a used RU has 242 tones or 106 tones, as illustrated inFIG. 10. Obviously, additional control information may be transmittedusing the other two cases in the HE ER SU PPDU.

If a HE ER SU PPDU is used, it may be configured that data is repeatedlytransmitted, for robust data transmission in an embodiment of thepresent disclosure. That is, available resources in the Data field ofthe HE ER SU PPDU may be divided into two parts and data may betransmitted by repeatedly transmitting the same information twice.

For example, if the HE ER SU PPDU is transmitted in a 106-tone RU, theavailable 106 tones may be divided by 52 tones, data may be mapped to 52tones, and the same data may be mapped to the remaining 52 tones, forrepeated transmission.

For this purpose, HE-SIG A may include 1-bit control informationindicating whether the above-described repeated transmission scheme isapplied.

Dual carrier modulation (DCM) may be used as an example of the repeatedtransmission scheme. DCM may be regarded as repeated modulation of thesame data to a pair of tones. However, when the same data is repeated,the second transmission data may be transmitted by phase rotation at apredetermined angle or conjugation.

FIG. 11 is a view illustrating the concept of including, in HE-SIG A, afield indicating whether a repeated transmission scheme is applied to aData field of a HE ER SU PPDU according to an embodiment of the presentdisclosure.

While FIG. 11 illustrates DCM as the repeated transmission scheme by wayof example, the repeated transmission scheme is not limited to DCM.

Referring to FIG. 11, a 1-bit DCM field indicates whether DCM is appliedto the Data field by values 1 and 0. Since DCM is intended for robusttransmission, DCM is preferably restricted to MCS levels equal to orlower than a predetermined level. In the example of FIG. 11, DCM isapplied restrictively to MCS0, MCS1, MCS3, and MCS4. Further, DCM islimited to one or two spatial streams (SSs), not applied to space andtime block code (STBC) in FIG. 11.

As described before, a HE SU PPDU indicates an MCS level using 4-bitinformation of HE-SIG A. In general, the HE SU PPDU may represent MCElevel 0 to MCS level 11 by the 4-bit information. On the other hand, theHE ER SU PPDU according to the embodiment of the present disclosure mayuse only the three lowest MCS levels for robust transmission withminimal signaling. Thus, the MCS field of HE-SIG A may be simplified inthe HE ER SU PPDU.

FIG. 12 is a view illustrating MCS information in HE-SIG A of a HE ER SUPPDU according to an embodiment of the present disclosure.

Referring to FIG. 12, the HE SU PPDU may indicate MCS level 0 to MCSlevel 11 using all of 4-bit information, whereas the HE ER SU PPDU mayindicate only MCS0, MCS1, and MCS2.

More specifically, if 242 tones are used for transmission of the HE ERSU PPDU, one of MCS0, MCS1, and MCS2 is indicated, and if 106 tones areused for transmission of the HE ER SU PPDU, MCS0 is fixedly used.

FIGS. 10, 11, and 12 are purely exemplary, and specific formats may bedifferent from those illustrated in FIGS. 10, 11, and 12. Because the HEER SU PPDU uses fewer bits than the HE SU PPDU, the HE ER SU PPDU mayrepresent additional control information by means of the remaining extrabits.

The above method for using 106 tones/242 tones at a fixed position isnot the only embodiment of the present disclosure, and other alternativeembodiments will be described below.

Embodiments Using Different Structures

A HE ER SU PPDU may be transmitted in an RU at a changed position,compared to the foregoing embodiment. The following examples may beconsidered.

(1) Best Band Selection with Power Boosting

As illustrated in [Table 1], when an RU size or type different from the242-tone RU type is used, there are a plurality of RUs of the same sizein 20 MHz. Therefore, a channel state and interference may varyaccording to the positions of RUs in a BW. Thus, once one RU size isselected from a given RU set, an RU location having a minimal channelinfluence and a minimal interference influence is selected for RUtransmission and data is transmitted in an RU at the selected position.The signal transmitted in the RU is transmitted with power boosted asmuch as the number of RUs of the RU size.

For example, if the 106-tone RU type is used, there are two 106-tone RUsin 20 MHz. If the upper 106-tone RU is in a better channel state thanthe lower 106-tone RU, a signal is transmitted in the upper 106-tone RU.Since the signal is transmitted only one of the two RUs, the signal maybe transmitted with power boosting. Accordingly, the power of thetransmitted signal may be boosted by at least twice (3 dB) up to 3dB+alpha in consideration of extra power available by not using central26 tones.

(2) Repetition within 20 MHz

Once an RU size or type is determined for signal transmission, data istransmitted using the RU size. Herein, the data is repeatedlytransmitted in RUs of the determined RU size in 20 MHz. For example, ifthe 52-tone RU type is used, there are four 52-tone RUs in 20 MHz, andthus the same data is repeatedly transmitted in the four 52-tone RUs.

Owing to repeated transmissions of the same data in RUs of the samesize, diversity and repetition gains may be achieved.

Further, data may be repeated within a selected RU size. Data isrepeated, each time in an RU size smaller than a given RU size fortransmission. For example, if a signal is transmitted in a 106-tone RU,data is repeatedly transmitted, each time in an RU size of 52 tones.

An RU size for ER transmission is preferably equal to or larger than 52tones. A transmission RU configured by repeating data in a smaller RUsize may be transmitted in 20 MHz in Method 1, Method 2, or Method 3.

Further, a method for selecting an optimum band and an optimum RU sizeat the same time may be applied.

That is, a band or RU size in a good channel state with lessinterference is selected. Data is transmitted using the selected RUsize. Specifically, the data is repeatedly transmitted in an RU sizesmaller than the selected RU size. For example, if an RU size used fortransmission is 106 tones, a better RU between two 106-tone RUs isselected, and data is loaded in a 52-tone RU smaller than the RU size.The data is repeated on an 52-tone RU basis and thus transmitted in the106-tone RU. The signal in the 106-tone RU is transmitted with powerboosting as described in (1).

To transmit an ER PPDU using various RU sizes in the above manner,information about a transmission RU size or type or information about anRU size should be transmitted in HE-SIG A. Therefore, HE-SIG A includedin the ER PPDU may be configured based on information of HE-SIG Aincluded in an SU PPDU, as follows.

RU information for transmission of a HE SU ER PPDU may be indicated bymodifying a part of the fields included in HE-SIG A of a legacy SU PPDU,in consideration of the afore-described remaining bits (e.g., 2 bits) ofHE-SIG A in a HE SU PPDU, and the following ER transmission situations.

If a signal is transmitted based on best band selection with powerboosting, an indication is made through HE-SIG A, as follows.

Case of Using Method 1

An RU size used for ER PPDU transmission may be indicated using reservedbits (i.e., 2 bits) of HE-SIG A in a HE SU PPDU. For example, if RUsizes available for transmission are 26, 52, 106, and 242 tones, a usedRU size may be indicated using 2-bit information as follows.

TABLE 2 2 bit indices RU size 00  52 01 106 10 242 11 Reserved (26)

The above table is exemplary. Since four RU sizes are available, 2 bitsare used. According to an RU size configuration used for transmission,each index may indicate a different RU size.

Since an ER PPDU is always transmitted in one SS, Nsts informationincluded in HE-SIG A of a HE SU PPDU is not needed. Therefore, sinceinformation about an RU size used for transmission is transmitted in afield defined in the above example, the position of an RU carrying datamay be determined, considering that the Nsts field indicates an RUallocation in ER transmission.

For example, each RU forms 20 MHz as illustrated in FIG. 9. In anembodiment of the present disclosure, it is assumed that RU locationsare indicated sequentially from the left of the drawing. That is, it maybe assumed that RUs are indicated in an order of low to high frequencyindexes. This is a mere example, and thus ordering of positions is notlimited in the present disclosure.

Thus, 3-bit allocation information may be configured as follows.

TABLE 3 3 Bit indices Allocation of RU 000 First 001 Second 010 Third011 4^(th) 100 5^(th) 101 6^(th) 110 7^(th) 111 8^(th)

Therefore, once an RU size is determined, each RU location is indicatedas illustrated in [Table 4].

TABLE 4 3 Bit Allocation of RU indices 26 tone RU 52 tone RU 106 tone RU000 1^(st ) 1^(st)  1^(st)  001  2^(nd) 2^(nd) 2^(nd) 010 3^(rd) 3^(rd )x 011 4^(th) 4^(th ) x 100 5^(th) x x 101 6^(th) x x 110 7^(th) x x 1118^(th) x x x: non-use of the indication for a specific RU size.

The number of bits used for the allocation information may be changedaccording to a minimum RU size used for transmission. For example, ifall RU sizes are available, 26-tone RUs are at most positions. Since thenumber of 26-tone RUs except for central 26 tones is 8, an RU locationmay be indicated in 3 bits. Regarding other RU sizes except the 26-toneRU size, however, if the 52-tone RU size is used, there are four 52-toneRUs. Then, an RU location may be indicated only in 2 bits. If theminimum RU size is 106 tones, an RU location may be indicated in 1 bit.

[Table 5] below illustrates a case with a minimum RU size of 52 tones,and [Table 6] below illustrates a case with a minimum RU size of 106tones.

TABLE 5 2 Bit indices Allocation of RU 00 1^(st)  01 2^(nd) 10 3^(rd )11 4^(th )

TABLE 6 1 Bit indices Allocation of RU 0 1^(st)  1 2^(nd)

FIG. 13 is a table illustrating a structure of HE-SIG A in a HE ER SUPPDU according to an embodiment of the present disclosure.

Specifically, FIG. 13 illustrates HE-SIG A configured based on thedescription given with reference to [Table 2] to [Table 6].

In FIG. 13, reference numeral 1310 denotes use of 2 reserved bits in aHE SU PPDU, and reference numeral 1320 denotes reuse of an Nsts field ina HE SU PPDU.

As illustrated in FIG. 13, information needed for transmission of a HEER SU PPDU may be transmitted in a field unnecessary for the HE ER SUPPDU among the fields of HE-SIG A in a HE SU PPDU.

FIG. 14 is a block diagram of apparatuses for performing theabove-described methods.

Referring to FIG. 14, a wireless apparatus 100 may be theafore-described specific STA, and a wireless apparatus 150 may be theafore-described AP.

The STA 100 may include a processor 110, a memory 120, and a transceiver130. The AP 150 may include a processor 160, a memory 170, and atransceiver 180. The transceivers 130 and 180 may transmit and receivewireless signals and may be implemented in an IEEE 802.11/3GPP physicallayer. The processors 110 and 160 may be implemented in the physicallayer and/or the MAC layer and connected to the transceivers 130 and180. The processors 110 and 160 may perform the forgoing HE ER SU PPDUtransmission/reception.

The processors 110 and 160 and/or the transceivers 130 and 180 mayinclude Application-Specific Integrated Circuit (ASICs), other chipsets, logic circuits, and/or data processors. The memories 120 and 170may include read only memories (ROMs), random access memories (RAMs),flash memories, memory cards, storage media, and/or other storage units.If an embodiment is implemented in software, the above-described methodsmay be performed in a module (e.g., a process or a function) performingthe afore-described functions. The module may be stored in the memories120 and 160 and executed by the processors 110 and 160. The memories 120and 170 may reside inside or outside the processors 110 and 160 and maybe connected to the processors 110 and 160 by well-known means.

As is apparent from the foregoing description, a STA can efficientlyconfigure and transmit/receive a HE ER SU PPDU for robust transmissionaccording to an embodiment of the present disclosure.

While the present disclosure has been described above in the context ofan IEEE 802.11 WLAN system, the present disclosure is not limitedthereto. The present disclosure is applicable in the same manner tovarious wireless systems.

The detailed description of the preferred embodiments of the presentdisclosure has been given to enable those skilled in the art toimplement and practice the present disclosure. Although the presentdisclosure has been described with reference to the preferredembodiments, those skilled in the art will appreciate that variousmodifications and variations can be made in the present disclosurewithout departing from the spirit or scope of the present disclosuredescribed in the appended claims. Accordingly, the present disclosureshould not be limited to the specific embodiments described herein, butshould be accorded the broadest scope consistent with the principles andnovel features disclosed herein.

What is claimed is:
 1. A method for transmitting data by a first station(STA) in a wireless local area network (WLAN) system, the methodcomprising: configuring, as a radio frame for transmission of the data,a high efficiency extended range single user physical protocol data unit(HE ER SU PPDU) in which a high efficiency signal A (HE-SIG-A) field isrepeated; and transmitting the configured HE ER SU PPDU to a second STAin a resource unit (RU) of one of a first type and a second type, thefirst type having a size of 106 tones and the second type having a sizeof 242 tones, wherein if the HE ER SU PPDU is transmitted in an RU ofthe first type, the HE ER SU PPDU is transmitted in an RU of the firsttype at a fixed position in a primary 20-MHz channel.
 2. The methodaccording to claim 1, wherein the radio frame for transmission of thedata includes a HE single user (SU) PPDU, a HE multi-user (MU) PPDU, anda HE trigger-based PPDU in addition to the HE ER SU PPDU, and wherein ifthe data is transmitted in the HE MU PPDU or the HE trigger-based PPDU,an RU of a third type having a size of 26 tones and an RU of a fourthtype having a size of 52 tones are used in addition to an RU of thefirst type and an RU of the second type.
 3. The method according toclaim 2, wherein if the data is transmitted in the HE ER SU PPDU, an RUof the third type and an RU of the fourth type are not used.
 4. Themethod according to claim 2, wherein if the data is transmitted in theHE SU PPDU, a bandwidth (BW) field of the HE-SIG A field indicates atransmission BW of the HE SU PPDU among BWs being multiples of 20 MHz,and wherein if the data is transmitted in the HE ER SU PPDU, the BWfield of the HE-SIG A field indicates whether the HE ER SU PPDU uses anRU of the first type or an RU of the second type.
 5. The methodaccording to claim 1, wherein the data is transmitted in a data field ofthe HE ER SU PPDU in a repeated transmission scheme in which availableresources of the data field are divided into two parts and the sameinformation is repeatedly transmitted twice.
 6. The method according toclaim 5, wherein the HE-SIG A field includes a 1-bit field indicatingwhether the repeated transmission scheme is applied to the data field.7. The method according to claim 2, wherein if the data is transmittedin the HE SU PPDU, a modulation and coding scheme (MCS) field of theHE-SIG A field indicates an applied MCS level in 4 bits, and wherein ifthe data is transmitted in the HE ER SU PPDU, the MCS field of theHE-SIG A field represents only three or fewer MCS levels.
 8. A station(STA) for transmitting data in a wireless local area network (WLAN)system, the STA comprising: a processor for configuring, as a radioframe for transmission of the data, a high efficiency extended rangesingle user physical protocol data unit (HE ER SU PPDU) in which a highefficiency signal A (HE-SIG-A) field is repeated; and a transceiver fortransmitting the configured HE ER SU PPDU, wherein the transceivertransmits the HE ER SU PPDU in a resource unit (RU) of one of a firsttype and a second type, the first type having a size of 106 tones andthe second type having a size of 242 tones, and if the HE ER SU PPDU istransmitted in an RU of the first type, the processor controlstransmission of the HE ER SU PPDU in an RU of the first type at a fixedposition in a primary 20-MHz channel.
 9. The STA according to claim 8,wherein the radio frame for transmission of the data includes a HEsingle user (SU) PPDU, a HE multi-user (MU) PPDU, and a HE trigger-basedPPDU in addition to the HE ER SU PPDU, and wherein if the data istransmitted in the HE MU PPDU or the HE trigger-based PPDU, theprocessor uses an RU of a third type having a size of 26 tones and an RUof a fourth type having a size of 52 tones in addition to an RU of thefirst type and an RU of the second type.
 10. The STA according to claim9, wherein if the data is transmitted in the HE ER SU PPDU, theprocessor does not use an RU of the third type and an RU of the fourthtype.
 11. The STA according to claim 9, wherein if the data istransmitted in the HE SU PPDU, a bandwidth (BW) field of the HE-SIG Afield indicates a transmission BW of the HE SU PPDU among BWs beingmultiples of 20 MHz, and wherein if the data is transmitted in the HE ERSU PPDU, the BW field of the HE-SIG A field indicates whether the HE ERSU PPDU uses an RU of the first type or an RU of the second type. 12.The STA according to claim 8, wherein the processor transmits the datain a data field of the HE ER SU PPDU in a repeated transmission schemein which available resources of the data field are divided into twoparts and the same information is repeatedly transmitted twice.
 13. TheSTA according to claim 12, wherein the HE-SIG A field includes a 1-bitfield indicating whether the repeated transmission scheme is applied tothe data field.
 14. The STA according to claim 8, wherein if the data istransmitted in the HE SU PPDU, a modulation and coding scheme (MCS)field of the HE-SIG A field indicates an applied MCS level in 4 bits,and wherein if the data is transmitted in the HE ER SU PPDU, the MCSfield of the HE-SIG A field represents only three or fewer MCS levels.